Fault tolerant modem redundancy

ABSTRACT

A fault tolerant modem system is provided according to some embodiments of the invention. A modem can include modulators and/or demodulators that provide redundancy in the event one of the modulators and/or demodulators fail. Connectivity between modulators and demodulators, for example, can be used to propagate TDMA timing to connected modulators and/or demodulators. Moreover, redundancy can be provided using modulators and/or demodulators with three or more input/output ports.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the benefit of commonly assigned U.S. Provisional Patent Application No. 61/056,425, filed May 27, 2008, entitled “Return Link Power Control and Fault Tolerant Modem Redundancy,” and this application claims the benefit of commonly assigned U.S. Provisional Patent Application No. 61/056,772, filed May 28, 2008, entitled “Time of Day Encryption Using TDMA Timing,” the disclosures of which are herein incorporated by reference for all purposes.

BACKGROUND

A modem is a device that modulates an analog carrier signal to encode digital information, and also demodulates a similar carrier signal to decode the transmitted information. Modems can include a single modulator and/or demodulator as well as multiple modulators and/or demodulators. For example, in large communication networks such as satellite networks or mobile telephone networks, a modem may include multiple modulators and demodulators. Modems typically produce a signal that can be transmitted easily and decoded to reproduce the original digital data.

Direct broadcast satellite, WiFi, and mobile phones all typically use modems to communicate. Modern telecommunications and data networks can use radio modems where long distance data links are required. Modems can also be used to allow multiple users to access a communication channel through frequency-division multiple access or time division multiple access (TDMA) techniques. Wireless modems can come in a variety of types, bandwidths, and/or speeds. Wireless modems can transmit information that is modulated onto a carrier frequency to allow many simultaneous wireless communication links to work simultaneously on different frequencies.

BRIEF SUMMARY

In some embodiments of the invention, the present disclosure provides for a redundant modulator and/or demodulator distribution. For example, 1:1 up to and beyond 1:4 modulator and/or demodulator redundancy can be supported. As another example, 1:1 up to 1:∞demodulators can be supported. That is, 1:2, 1:3, 1:10, 1:32, 1:50, 1:64, 1:100, etc. modulators and/or demodulators can be supported without damaging the redundancy scheme. As another example, multiple 1:1 up to 1:∞demodulators can be employed. For example, two 1:2 demodulators that can support 4 online demodulators and 2 redundant demodulators, five 1:4 demodulators to support 20 online demodulators with 4 redundant demodulators, fifty 1:6 demodulators to support 300 online demodulators and 50 redundant demodulators, etc.

Some embodiments of the invention provide for modulator and/or demodulator redundancy in a modem. In some embodiments, modulators and demodulators can be connected together to propagate synchronized timing data that is used for modulation and/or demodulation. Connection schemes are provided that allow one failure in any redundancy group of modulator(s) and/or demodulator(s), yet still maintain synchronized timing between all remaining operational modulators and demodulators. Moreover, modulators and/or demodulators used in some embodiments can include three or four input/output ports for communicating timing information.

Further areas of applicability of the present disclosure will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating various embodiments, are intended for purposes of illustration only and do not limit the scope of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a satellite communication system according to some embodiments.

FIG. 2 shows a connection diagram with a modulator and demodulator with a redundant modulator according to some embodiments.

FIG. 3 shows a connection diagram with a modulator and two demodulators with a redundant modulator according to some embodiments.

FIG. 4 shows a connection diagram with a modulator and three demodulators with a redundant modulator according to some embodiments.

FIG. 5 shows a connection diagram with a modulator and five demodulators with a redundant modulator according to some embodiments.

FIG. 6 shows a connection diagram with two modulators and two groups of two demodulators with a redundant modulator according to some embodiments.

FIG. 7 shows a connection diagram with two modulators and two groups of five demodulators with a redundant modulator according to some embodiments.

FIG. 8 shows a connection diagram with three modulators and three groups of two demodulators with a redundant modulator according to some embodiments.

FIG. 9 shows a connection diagram with three modulators and three groups of five demodulators with a redundant modulator according to some embodiments.

FIG. 10 shows a connection diagram with four modulators and four demodulators with a redundant modulator according to some embodiments.

FIG. 11 shows a connection diagram with four modulators and four groups of two demodulators with a redundant modulator according to some embodiments.

FIG. 12 shows a connection diagram with four modulators and four groups of three demodulators with a redundant modulator according to some embodiments.

FIG. 13 shows a connection diagram with four modulators and four groups of five demodulators with a redundant modulator according to some embodiments.

FIG. 14 shows a connection diagram with four modulators and twelve groups of five demodulators with a redundant modulator according to some embodiments.

DETAILED DESCRIPTION

Embodiments of the present invention can provide 1 to N modulator redundancy and/or demodulator redundancy in a communication network such as a satellite network. In some embodiments a communication hub (e.g., transceiver and/or modem) can include a plurality of modulators that can be employed to modulate data onto a communication channel for transmission to terminals throughout the network. In some embodiments, the hub can also include a plurality of demodulators that can also be employed to demodulate the signals received from the terminals. Ensuring synchronization of timing from modulators to modulator and to demodulators can be a priority of such communication systems. For example, in a TDMA network, various terminals can communicate with the hub using assigned timeslots in a single channel. To ensure timeslot synchronization, timing between modulators and demodulators can be required.

Embodiments of the present invention couple demodulators and/or modulators to allow failure of one or more of the modulators and/or demodulators without loss of timing synchronization. Moreover, in some embodiments, demodulators and/or modulators can provide 1 to N redundancy while only including three or four input/output ports on the modulators and/or demodulators. Such embodiments allow for failures and hot swapping of modulators and/or demodulators without losing data and/or without losing timing. Moreover, embodiments described herein can provide redundancy with three or more input/output ports on any one modulator and/or demodulator.

Some embodiments of the invention can be particularly useful for communication in a satellite network and in particular as part of the hub of a satellite network. FIG. 1 shows satellite system 100 that is an example of a satellite system that can implement various embodiments of the invention. As shown, hub (or network controller) 115 can communicate with various subscriber terminals 130 through satellite 105. In this embodiment, hub 115 is coupled with communication network 120, for example, the Internet. In some embodiments, communication network 120 can include a private computer network, a computer system, and/or servers. Hub 115 can use a satellite dish 110 (e.g., an antenna and/or a parabolic antenna) to bi-directionally communicate with a satellite 105 on a feeder link. An upstream forward link 135 communicates information from the hub 115 to satellite 105, and downstream return link 140 communicates information from satellite 105 to hub 115. Although not shown, there may be a number of gateways 115 in system 100. In some embodiments, hub 115 can also include one or more computer processing systems including, for example, a processor, controller, memory, network interfaces, etc. In some embodiments, hub 115 can include the computational system shown in FIG. 3.

Satellite 105 could perform switching or be a bent-pipe. Information can bi-directionally pass through the satellite 105. Satellite 105 could use antennas or phased arrays when communicating. The communication could be focused into spot beams or more broadly cover a bigger geographical area, for example, the entire continental US (CONUS).

Subscriber terminal 130 in this example can be bi-directionally coupled with satellite 105 and can provide connectivity with network 120 through hub 115. Subscriber terminal 130 can receive information with forward downlink 150 from satellite 105, and transmit information that is sent on a number of return uplinks 145. Subscriber terminal 130 can initiate return uplink 145 to send information upstream to satellite 105 and ultimately the hub 115.

Communication channels such as downstream downlink 150, upstream uplink 145, downstream return link 140, and/or downstream uplink 135, can include Ka band, Ku band, X band and/or C band.

In some embodiments, communication controller 115 (or hub or hub) can include a plurality of modulators and/or demodulators. The modulators can receive a digital bit stream and modulate the digital bit stream onto a carrier channel. The demodulators can receive a signal from a terminal 130 and demodulate a digital bit stream therefrom. In some communication networks, such as TDMA or MFTDMA networks, timing between modulators and/or demodulators can be important. Various schemes have been devised to ensure timing is propagated from modulator to modulator, from modulator to demodulator, demodulator to demodulator, timing source to modulator and/or timing source to demodulator. In some embodiments of the invention, timing is propagated through a system of modulators and demodulators while providing redundancy and/or while using modulators and/or demodulators with as few as three input/output communication ports to propagate timing.

FIG. 2 shows connection diagram 200 with modulator 205 and demodulator 250 with redundant modulator 210 according to some embodiments. Modulator 205 is shown connected with demodulator 250. Redundant modulator 210 is also shown being connected with demodulator 250. The connections between modulators 205, 210 and demodulator 250 can be made using any type of cable or connectors known in the art without limitation. Modulator 205 and/or modulator 210 can also be coupled with a timing source such as a GPS receiver, an oscillator, a clock, or any other device that can provide timing to the modulators 205, 210. Timing can then be passed from modulator 205 or modulator 210 to demodulator 250 through the connections shown in diagram 200. Modulator 205 can provide timing to demodulator 250. In the event there is a failure with modulator 205 and/or the cable providing a connection between modulator 205 and demodulator 250, then modulator 210 can be used and timing can still propagate to demodulator 250 from redundant modulator 210. While each modulator 205, 210 and demodulator 250 shown in connection with diagram 200 have four input/output ports, in some embodiments, each modulator 205, 210 and demodulator 250 can include two or three input/output ports. Various other redundancies not explicitly described can also be achieved with connection diagram 200.

FIG. 3 shows connection diagram 300 with modulator 305 and two demodulators 350, 351 with redundant modulator 310 according to some embodiments. Modulator 305 is shown connected with demodulator 350 and demodulator 351. Redundant modulator 310 is also shown being connected with demodulator 350 and demodulator 351. Demodulator 350 is also coupled with demodulator 351. Modulator 305 and/or redundant modulator 310 can also be coupled with a timing source such as a GPS receiver, an oscillator, a clock, or any other device that can provide timing to the modulators 305, 310. The connections between modulators 305, 310 and demodulators 350, 351, can be made using any type of cable or connectors known in the art without limitation. For example, connections can be provided using CAT-5 Ethernet cables. Timing can then be passed from modulator 305 and/or redundant modulator 310 to demodulator 350 or demodulator 351 through the connections shown in diagram 300.

Modulator 305 can provide timing to demodulator 350 and demodulator 351 through their respective connections. In the event there is a failure with the connection between modulator 305 and demodulator 350 then timing will propagate to demodulator 350 from its connection with demodulator 351. Similar redundancy is provided if there is a failure with the connection between modulator 305 and demodulator 351. In the event there is a failure with modulator 305 then modulator 310 can be used and timing can still be propagated to demodulator 350 and demodulator 351 from redundant modulator 310. Since each demodulator obtains timing from an independent connection to each modulator, either demodulator can fail without affecting the other demodulator timing path. While each modulator 305, 310 and demodulator 350, 351 shown in connection with diagram 300 have four input/output ports, in some embodiments, each modulator 305, 310 and demodulator 350 can include three input/output ports. Various other redundancies not explicitly described can also be achieved with connection diagram 300.

FIG. 4 shows connection diagram 400 with modulator 405 and three demodulators 450, 451, 452 with redundant modulator 410 according to some embodiments. Any one of the three demodulators can be the redundant unit. In this embodiment, modulator 405 is coupled with demodulator 450 and demodulator 452. Redundant modulator 410 is coupled with demodulator 450 and demodulator 451. Moreover, demodulator 451 is coupled to both demodulator 450 and demodulator 452. Each demodulator 450, 451, 452 can include three or more input/output ports. Modulator 405 and modulator 410 can each include two or more input/output ports. Timing normally propagates from modulator 405 to demodulators 450 and 452 then from demodulator 451 to 452. Modulator 405 and/or redundant modulator 410 can also be coupled with a timing source such as a GPS receiver, an oscillator, a clock, or any other device that can provide timing to the modulators 405, 410.

Various redundancies are provided in connection with diagram 400. Demodulator 450 can fail or the connection between modulator 405 and demodulator 450 can fail and timing will propagate from modulator 405 to demodulator 452 and then to demodulator 451 and demodulator 450. Similar redundancy can be provided if demodulator 452 fails or the connection between modulator 405 and demodulator 452 fails. The connection between demodulator 450 and demodulator 451 can fail and timing can propagate from modulator 405 to demodulator 450 and demodulator 452 and then from demodulator 452 to demodulator 451. Similar redundancy can be provided if the connection between demodulator 451 and demodulator 452 fail. Modulator 405 can fail and redundant modulator 410 can provide timing to demodulator 450 and demodulator 451, and then to demodulator 452. Both modulator 405 and demodulator 450 can fail and timing will propagate from modulator 410 to demodulator 451 then to 452. Various other redundancies not explicitly described can also be achieved with connection diagram 400.

FIG. 5 shows connection diagram 500 of a modulator 505 and five demodulators 550, 551, 552, 553, 554 with redundant modulator 510 according to some embodiments. Any one of the five demodulators may be the redundant unit. In this embodiment, modulator 505 is coupled with demodulator 550 and demodulator 553. Redundant modulator 510 is coupled with demodulator 551 and demodulator 552. Each demodulator is coupled with two adjacent demodulators in a daisy chain fashion. Timing normally propagates from modulator 505 to demodulators 550 and then via the daisy chain to demodulators 551, 552, 553, 554. Modulator 505 and/or redundant modulator 510 can also be coupled with a timing source such as a GPS receiver, an oscillator, a clock, or any other device that can provide timing to the modulators 505, 510.

Various redundancies can be provided in systems that implement connection diagram 500. Modulator 505 can fail, and timing can be propagated to demodulator 551 or 552 from modulator 510 and then propagated to the other demodulators through the daisy chain of demodulators. The cable connecting modulator 505 and demodulator 550 can fail and timing can still propagate from modulator 505 to demodulator 553 and then propagate to the other demodulators through the daisy chain of demodulators. Similar redundancy is provided if the cable between modulator 505 and demodulator 553 fails. Furthermore, if demodulator 550 fails, then timing can propagate to demodulator 553 from modulator 505 and then propagate to the other demodulators through the daisy chain of demodulators. If demodulator 553 fails, then timing can propagate to demodulator 550 from modulator 505 and then propagate the timing to the other demodulators through the daisy chain of demodulators. If modulator 553 fails, then timing propagates from modulator 505 to demodulator 550 and then propagate to the other demodulators through the daisy chain of demodulators. Various other redundancies not explicitly described can also be achieved with connection diagram 500.

FIG. 6 shows connection diagram 600 of two modulators 605, 606 and two groups of demodulators 640, 645, each group with two demodulators and with redundant modulator 610 according to some embodiments. Modulator 605 is connected with demodulators 651 and 652, which are in demodulator group 640. Demodulator 651 is also connected with demodulator 652. Modulator 606 is connected with demodulators 661 and 662, which are in demodulator group 645. Demodulator 661 is also connected with demodulator 662. Moreover, modulator 605 is also coupled with demodulator 662 and modulator 606 is coupled with demodulator 652. Furthermore, redundant modulator 610 is coupled with demodulator 651 and demodulator 661. Modulator 605, modulator 606 and/or redundant modulator 610 can also be coupled with a timing source such as a GPS receiver, an oscillator, a clock, or any other device that can provide timing to the modulators 605, 606, 610.

Various redundancies are provided in systems that implement connection diagram 600. Modulator redundancy is provided by redundant modulator 610, so that timing can be sent to each group of demodulators 640, 645 in the event that modulator 605 or modulator 606 fails. Modulator redundancy is also provided by connecting modulator 605 with a demodulator in both groups of demodulators 640, 645 and by connecting modulator 606 with a demodulator in both groups of demodulators 640, 645. Any one modulator or demodulator shown in the figure can fail and timing can still propagate to every modulator and/or demodulator. Yet, each modulator and/or demodulator has three or more input/output ports. Various other redundancies not explicitly described can also be achieved by implementing connection diagram 600.

FIG. 7 shows connection diagram 700 with two modulators 705, 706 and two groups of five demodulators 740, 745 with redundant modulator 710 according to some embodiments. Modulator 705 is coupled with demodulator 751. In some embodiments, modulator 705 can be coupled with another demodulator in group 740 and/or coupled with a different demodulator within group 740. Modulator 706 is coupled with demodulator 761. In some embodiments, modulator 706 can be coupled with another demodulator in group 745 and/or coupled with a different demodulator within group 745. Modulator 705 is also coupled with demodulator 763 or any other demodulator in demodulator group 745. Modulator 706 is also coupled with demodulator 753 or any other demodulator in demodulator group 740. Redundant modulator 710 can also be coupled with demodulator 752 and/or demodulator 762 or any other demodulator in the respective demodulator groups. Each demodulator in each demodulator group 640, 645 is connected to two other demodulators in a daisy chain fashion. In some embodiments, each demodulator includes only three input/output ports and/or each modulator includes only two input/output ports. Modulator 705, modulator 706 and/or redundant modulator 710 can also be coupled with a timing source such as a GPS receiver, an oscillator, a clock, or any other device that can provide timing to the modulators 705, 706, 710.

Various redundancies can be achieved by systems implementing connection diagram 700. Any of the five demodulators in each group of demodulators can fail and timing can still be propagated to each of the remaining demodulators. For example, if demodulator 751 fails, then timing can be received at demodulator 752 from redundant modulator 710 and/or at demodulator 753 from modulator 706. If timing is received at any demodulator the timing can propagate to every other demodulator in the group through the daisy chain of interconnected demodulators and can do so even if one demodulator fails. As another example, if demodulator 761 fails, then timing can be received at demodulator 762 from redundant modulator 710 and/or at demodulator 763 from modulator 705. Various other redundancies not explicitly described can also be achieved by implementing connection diagram 700.

FIG. 8 shows connection diagram 800 with three modulators 805, 806, 807 and three groups 841, 842, 843 each with two demodulators and with redundant modulator 810 according to some embodiments. In this embodiment, modulator 805 is coupled with demodulator 851, demodulator 872 and redundant modulator 810. In this embodiment, modulator 806 is coupled with demodulator 861, demodulator 852, and redundant modulator 810. In this embodiment, modulator 807 is coupled with demodulator 871, demodulator 862, and redundant modulator 810. Each demodulator can be connected with each demodulator in each group. Modulator 805, modulator 806, modulator 807, and/or redundant modulator 810 can also be coupled with a timing source such as a GPS receiver, an oscillator, a clock, or any other device that can provide timing to the modulators 805, 806, 807, 810.

As discussed in regard to previous configurations, modulator and/or demodulator failure can occur without loss of timing to any of the modulators and/or demodulators. For example, any of modulators 805, 806, 807 can fail and redundant modulator 801 and/or a neighboring modulator can provide timing. It should also be noted that in this embodiment, the modulators and/or demodulators can be equipped with three or more input/output ports. Various other redundancies not explicitly described can also be achieved by implementing connection diagram 800.

FIG. 9 shows connection diagram 900 with three modulators and three groups 941, 942, 943 of five demodulators with redundant modulator 910 according to some embodiments. In this embodiment, modulator 905 is coupled with demodulator 951 and demodulator 973. In this embodiment, modulator 906 is coupled with demodulator 961 and demodulator 953. In this embodiment, modulator 907 is coupled with demodulator 971 and demodulator 963. Redundant modulator is connected with demodulator 952, demodulator 962 and demodulator 972. Each demodulator in the three demodulator groups are connected to both neighbor demodulators in a daisy chain fashion. Hence, timing can be passed from one demodulator to two neighboring demodulators. Modulators 905, 906, 907 and/or redundant modulator 910 can also be coupled with a timing source such as a GPS receiver, an oscillator, a clock, or any other device that can provide timing to the modulators 905, 906, 907, 910.

This embodiment of the invention provides timing propagation redundancy in the event any modulator or any demodulator fails. For example, if modulator 906 fails, the demodulators in demodulator group 942 can receive timing from either modulator 907 and/or redundant modulator 910 through the daisy chain of demodulators. As another example, if any demodulator in a group of demodulators fails, the rest of the demodulators can receive timing from one of it's neighbors with which it is connected. Various other redundancies not explicitly described can also be achieved by implementing connection diagram 900.

FIG. 10 shows connection diagram 1000 with four modulators 1005, 1006, 1007, 1008 and four demodulators 1051, 1061, 1071, 1081 with redundant modulator 1010 according to some embodiments. In this embodiment, modulator 1005 and redundant modulator 1010 are connected with demodulator 1051, modulator 1006 and redundant modulator 1010 are connected with demodulator 1061, modulator 1007 and redundant modulator 1010 are connected with demodulator 1071, and modulator 1008 and redundant modulator 1010 are connected with demodulator 1081. Each connection can provide timing from one device to another. In this embodiment, any of the modulators 1005, 1006, 1007, 1008 can fail and/or any connection between modulators 1005, 1006, 1007, 1008 and demodulators can fail and timing can still be transmitted to the demodulators. Moreover, each modulator 1005, 1006, 1007, 1008 can include one or more input/output ports. Each demodulator 1051, 1061, 1071, 108 can include two or more input/output ports. Redundant modulator 1010 can include four or more input/output ports. Modulators 1005, 1006, 1007, 1008 and/or redundant modulator 1010 can also be coupled with a timing source such as a GPS receiver, an oscillator, a clock, or any other device that can provide timing to the modulators 1005, 1006, 1007, 1008, 1010.

FIG. 11 shows connection diagram 1100 with four modulators 1105, 1106, 1107, 1108 and four groups of two demodulators with redundant modulator 1110 according to some embodiments. In this embodiment, modulator 1105 and redundant modulator 1110 are connected with demodulator 1151, modulator 1106 and redundant modulator 1110 are connected with demodulator 1161, modulator 1107 and redundant modulator 1110 are connected with demodulator 1171, and modulator 1108 and redundant modulator 1110 are connected with demodulator 1181. Modulator 1105 is also coupled with demodulator 1182 and demodulator 1152. Modulator 1106 is also coupled with demodulator 1152 and demodulator 1162. Modulator 1107 is also coupled with demodulator 1162 and demodulator 1172. Modulator 1108 is also coupled with demodulator 1182 and demodulator 1172. Each demodulator in the groups of demodulators can also be coupled with the other demodulator in the respective group. Moreover, each connection can provide TDMA timing from one device to another device. Redundant modulator 1010 can include four or more input/output ports. Modulators 1105, 1106, 1107, 1108 and/or redundant modulator 1110 can also be coupled with a timing source such as a GPS receiver, an oscillator, a clock, or any other device that can provide timing to the modulators 1105, 1106, 1107, 1108, 1110.

In this embodiment, any modulator 1105, 1106, 1107, 1108 can fail and timing can be provided to the groups of demodulators from another modulator and/or from redundant modulator 1110. Moreover, each demodulator in a group of demodulators can receive timing from a unique modulator. Hence, any one demodulator in a group can fail and the other demodulator in the group can still receive timing. Also, each modulator 1105, 1106, 1107, 1108 can include three or more input/output ports. Redundant modulator 1110 can include four input/output ports. Each demodulator can include three or more input/output ports.

FIG. 12 shows connection diagram 1200 with four modulators 1205, 1206, 1207, 1208 and four groups of three demodulators with redundant modulator 1210 according to some embodiments. In this embodiment, modulator 1205 is connected with demodulator 1251 and demodulator 1282. Modulator 1206 is connected with demodulator 1261 and demodulator 1252. Modulator 1207 is connected with demodulator 1271 and demodulator 1262. Modulator 1208 is connected with demodulator 1281 and demodulator 1272. Redundant modulator 1210 is coupled with demodulators 1253, 1263, 1273, 1283. Moreover, each demodulator is coupled with two other demodulator in its respective group in a daisy chain fashion. Redundant modulator 1210 can include four or more input/output ports. Modulators 1205, 1206, 1207, 1208 and/or redundant modulator 1210 can also be coupled with a timing source such as a GPS receiver, an oscillator, a clock, or any other device that can provide timing to the modulators 1205, 1206, 1207, 1208, 1210.

In this embodiment, any modulator can fail without loss of timing. Each group of demodulators can receive timing from one of three modulators. Moreover, each demodulator can receive timing from two demodulators as well as at least one modulator. Thus, demodulator failure without modulator failure will not result in a loss of timing at any other demodulator. Various other redundancies not explicitly described can also be achieved by implementing connection diagram 1200.

FIG. 13 shows connection diagram 1300 with four modulators 1305, 1306, 1307, 1308 and four groups of five demodulators with redundant modulator 1310 according to some embodiments. While five demodulators are shown in each group, any number of demodulators can be used without limitation. In this embodiment, demodulators in each group of demodulators 1341, 1342, 1343, 1344 can receive timing from three of the four modulators 1305, 1306, 1307, 1308 and redundant modulator 1310. Moreover, each of the demodulators within each group of demodulators are connected with two other demodulators in a daisy chain configuration. For example, in demodulator group 1341, demodulator 1351 is connected with demodulator 1352 and demodulator 1355; demodulator 1353 is connected with demodulator 1352 and demodulator 1354 and so forth. Thus, failure of any one demodulator in a group will not restrict the propagation of timing from the modulators. Furthermore, three modulators are connected with three different demodulators in each group of demodulators. If one of the modulators fail, timing can still be propagated to the demodulators using one of the other three demodulators. Various other redundancies not explicitly described can also be achieved by implementing connection diagram 1300. Redundant modulator 1310 can include four or more input/output ports. Modulators 1305, 1306, 1307, 1308 and/or redundant modulator 1310 can also be coupled with a timing source such as a GPS receiver, an oscillator, a clock, or any other device that can provide timing to the modulators 1305, 1306, 1307, 1308, 1310.

FIG. 14 shows connection diagram 1400 with four modulators 1410, 1411, 1412, 1413 and twelve groups of demodulators with redundant modulator 1410 according to some embodiments. Redundant modulator 1410 is coupled with each modulator 1405, 1406, 1407, 1408. Each group of demodulators in this embodiment includes five demodulators. Any number of demodulators can be included. Each demodulator in a group is coupled with at least two other demodulators in a daisy chain fashion.

Modulator 1410 is coupled with one demodulator in group 1451, one demodulator in group 1461, and one demodulator in group 1471. Modulator 1411 is coupled with one demodulator in group 1471, one demodulator in group 1461, and one demodulator in group 1481. Modulator 1412 is coupled with one demodulator in group 1451, one demodulator in group 1481, and one demodulator in group 1471. Modulator 1413 is coupled with one demodulator in group 1451, one demodulator in group 1461, and one demodulator in group 1481. Redundant modulator 1410 can include four or more input/output ports. Modulators 1405, 1406, 1407, 1408 and/or redundant modulator 1410 can also be coupled with a timing source such as a GPS receiver, an oscillator, a clock, or any other device that can provide timing to the modulators 1405, 1406, 1407, 1408, 1410.

As mentioned above, group 1451 is connected with three modulators. Accordingly, if any of the three modulators fail and/or the connection between the modulator and demodulator fail, timing can be propagated from one of the other modulators. Three of the demodulators in group 1451 are coupled with three demodulators in group 1452, and three of the demodulators in group 1452 are coupled with three demodulators in group 1453. Accordingly, if any demodulator in group 1451 fails, timing can still be transferred to each demodulator in group 1452. Likewise, if any demodulator in group 1452 fails, timing can still be transferred to each demodulator in group 1453. While the figures shows three groups of demodulators daisy chained together (e.g. demodulators 1451, 1452, 1453) any number of groups of demodulators can be daisy chained together as shown in the figure. Various other redundancies not explicitly described can also be achieved by implementing connection diagram 1400. Some of the demodulators and/or modulators shown in connection with diagram 1400 can include three or four or more input/output ports and still provide the redundancy discussed above.

In the description of various embodiments a connection between a modulator and/or a demodulator implies that timing data (e.g. TDMA time of day data and/or frame timing data) can be transferred from one modulator or demodulator to another modulator or demodulator and vice/versa. Each connection can be bi-directional and/or mono-direction. Thus, when a modulator is described as being connected with a demodulator the modulator can send and/or receive timing data to and/or from the demodulator. Moreover a connection between a modulator and/or demodulator to another modulator and/or demodulator can be made using any type of connector and/or cable. For example, connections can be made using CAT-5 or CAT-5e Ethernet cables. As another example, a connection can be made using a USB cables. Furthermore, an input/output port at a modulator and/or demodulator can include any type of communication port that can send and/or receive timing data. Thus, Ethernet and USB ports are examples of input/output ports.

In the description of embodiment of the invention a failure of a modulator and/or a demodulator can describe the failure of the modulator and/or demodulator to send timing data. For example, a modulator that loses power is a failed modulator and cannot send timing data. As another example, a defective cable or a misconnected cable between a modulator and a demodulator can be considered a failure of the modulator because the modulator cannot send timing data. Thus, any failure to transfer timing data from a first modulator and/or demodulator to a second modulator and/or demodulator can be considered a failure in the first modulator and/or demodulator.

Circuits, logic modules, processors, and/or other components may be described herein as being “configured” to perform various operations. Those skilled in the art will recognize that, depending on implementation, such configuration can be accomplished through design, setup, interconnection, and/or programming of the particular components and that, again depending on implementation, a configured component might or might not be reconfigurable for a different operation. For example, a programmable processor can be configured by providing suitable executable code; a dedicated logic circuit can be configured by suitably connecting logic gates and other circuit elements; and so on.

While various connection diagrams are described herein with reference to particular blocks, it is to be understood that the blocks are defined for convenience of description and are not intended to imply a particular physical arrangement of component parts. Further, the blocks need not correspond to physically distinct components.

While the embodiments described above may make reference to specific hardware and software components, those skilled in the art will appreciate that different combinations of hardware and/or software components may also be used and that particular operations described as being implemented in hardware might also be implemented in software or vice versa. 

1. A communication controller comprising: a first modulator; a redundant modulator; a first demodulator coupled with the first modulator and the redundant modulator, wherein the first demodulator is configured to receive timing information from the first modulator or the redundant modulator; and a second demodulator coupled with the first modulator, and the first demodulator, wherein the second demodulator is configured to receive timing information from the first demodulator or the first modulator.
 2. The communication controller according to claim 1, wherein the second demodulator is coupled with a redundant modulator and configured to receive timing information from the redundant modulator.
 3. The communication controller according to claim 1 further comprising: a second modulator; a third demodulator coupled with the second modulator and the redundant modulator, wherein the third demodulator is configured to receive timing information from the second modulator or the redundant modulator; and a fourth demodulator coupled with the second modulator, and the third demodulator, wherein the fourth demodulator is configured to receive timing information from the third demodulator or the second modulator.
 4. The communication controller according to claim 3, wherein the fourth modulator is coupled with the first modulator and configured to receive timing information from the first modulator.
 5. The communication controller according to claim 3, wherein the second modulator is coupled with the second modulator and configured to receive timing information from the second modulator.
 6. A communication controller comprising: a first modulator; a redundant modulator; and a first group demodulators comprising three or more demodulators, wherein each demodulator is coupled to at least one other demodulator within the first group of demodulators, wherein at least one demodulator is coupled with the first modulator and is configured to receive timing information from the first modulator, and wherein at least one demodulator is coupled with the redundant modulator and is configured to receive timing information from the redundant modulator.
 7. The communication controller according to claim 6, wherein two demodulators within the first group of demodulators are coupled with the first modulator and is configured to receive timing information from the first modulator.
 8. The communication controller according to claim 6, wherein two demodulators within the first group of demodulators are coupled with the redundant modulator and is configured to receive timing information from the redundant modulator.
 9. The communication controller according to claim 6, wherein each demodulator within the first group of demodulators is coupled with two other demodulators within the first group of demodulators.
 10. The communication controller according to claim 6, further comprising: a second modulator; and a second group of demodulators comprising three or more demodulators, wherein each demodulator is coupled to at least one other demodulator within the second group of demodulators, wherein at least one demodulator within the second group of demodulators is coupled with the second modulator and is configured to receive timing information from the second modulator, and wherein at least one demodulator within the second group of demodulators is coupled with the redundant modulator and is configured to receive timing information from the redundant modulator.
 11. The communication controller according to claim 10, wherein at least one demodulator within the second group of demodulators is coupled with the first modulator and is configured to receive timing information from the first modulator.
 12. The communication controller according to claim 10, wherein at least one demodulator within the first group of demodulators is coupled with the second modulator and is configured to receive timing information from the second modulator.
 13. The communication controller according to claim 10, further comprising: a third modulator; and a third group of demodulators comprising three or more demodulators, wherein each demodulator is coupled to at least one other demodulator within the third group of demodulators, wherein at least one demodulator within the third group of demodulators is coupled with the third modulator and is configured to receive timing information from the third modulator, and wherein at least one demodulator within the third group of demodulators is coupled with the redundant modulator and is configured to receive timing information from the redundant modulator.
 14. The communication controller according to claim 13, wherein at least one demodulator within the third group of demodulators is coupled with the first modulator and is configured to receive timing information from the first modulator.
 15. A communication controller comprising: a redundant modulator; a one or more modulators; and one or more groups of demodulators, wherein each group of demodulators comprises one or more demodulators, wherein at least one demodulator within each group of demodulators is coupled with the redundant modulator and configured to receive timing information from the redundant modulator, and wherein at least one demodulator within each group of demodulators is coupled with at least one of the one or more modulators and is configured to receive time of data information from the at least one of the one or more modulators.
 16. The communication controller according to claim 15, wherein at least one group of demodulators comprises a first demodulator coupled with a first modulator of the one or more modulators and is configured to receive timing information from the first modulator, and a second demodulator coupled with a second modulator of the one or more modulators distinct from the first modulator and is configured to receive timing information from the second modulator.
 17. The communication controller according to claim 15, wherein each group of demodulators comprises two or more demodulators, wherein each demodulator of the two or more demodulators is coupled with another demodulator within the group of demodulators.
 18. The communication controller according to claim 15, wherein each group of demodulators comprises three or more demodulators, wherein each demodulator of the three or more demodulators is coupled with two demodulators within the group of demodulators.
 19. A communication controller comprising: a redundant modulator; a first modulator; a first group of demodulators comprising two or more demodulators, wherein a demodulator within the first group of demodulators is coupled with the first modulator and configured to receive timing information from the first modulator, wherein a demodulator within the first group of demodulators is coupled with the redundant modulator and configured to receive timing information from the redundant modulator, wherein each demodulator within the first group of demodulators is coupled another demodulator within the group of demodulators; and a second group of demodulators comprising two or more demodulators, wherein a demodulator within the second group of demodulators is coupled with a demodulator in the first group of demodulators, wherein each demodulator within the second group of demodulators is coupled with another demodulator within the second group of demodulators.
 20. The communication controller according to claim 19 further comprising a second modulator, wherein the second modulator is coupled with at least one demodulator within the first group of demodulators.
 21. The communication controller according to claim 20 further comprising a third modulator, wherein the third modulator is coupled with at least one demodulator within the first group of demodulators.
 22. The communication controller according to claim 19 comprising a third group of demodulators comprising two or more demodulators, wherein a demodulator within the third group of demodulators is coupled with a demodulator in the second group of demodulators, wherein each demodulator within the third group of demodulators is coupled with another demodulator within the third group of demodulators
 23. The communication controller according to claim 19 wherein the first modulator is coupled with the redundant modulator.
 24. A communication controller comprising: a first modulator and a redundant modulator, wherein the first modulator is coupled with the redundant modulator and configured to receive time of day data from the redundant modulator; a first group of three or more demodulators, wherein each of the demodulators is coupled with two other demodulators within the first group of demodulators and is configured to receive timing information from the two other demodulators, and at least one of the demodulators is coupled with the first modulator and is configured to receive timing information from the first modulator; and a second group of demodulators wherein each of the demodulators is coupled with two other demodulators within the second group of demodulators and is configured to receive timing information from the two other demodulators, and at least one of the demodulators is coupled with a demodulator within the first group of demodulators and is configured to receive timing information from a demodulator within the first group of demodulators.
 25. The communication controller according to claim 24, further comprising a second modulator.
 26. The communication controller according to claim 25, wherein at least one demodulator within the first group of demodulators is coupled with the second modulator and configured to receive time of day data from the second demodulator.
 27. The communication controller according to claim 25 further comprising: a third group of demodulators wherein each of the demodulators is coupled with two other demodulators within the third group of demodulators and is configured to receive timing information from the two other demodulators, and at least one of the demodulators is coupled with the second modulator and is configured to receive timing information from the second modulator; and a fourth group of demodulators wherein each of the demodulators is coupled with two other demodulators within the fourth group of demodulators and is configured to receive timing information from the two other demodulators, and at least one of the demodulators is coupled with a demodulator within the third group of demodulators and is configured to receive timing information from a demodulator within the third group of demodulators. 